1. Field of the Invention
This invention relates generally to a method for monitoring the state of health and providing fault diagnosis for sensors in an integrated vehicle stability system and, more particularly, to a method for monitoring the state of health and providing fault diagnosis for sensors in an integrated vehicle stability system, where the method employs adaptive thresholds when comparing model based sensor output estimates and sensor measurements.
2. Discussion of the Related Art
Diagnostics monitoring for vehicle stability systems is an important vehicle design consideration to be able to quickly detect system faults, and isolate the faults for maintenance purposes. These stability systems typically employ various sensors, including yaw rate sensors, lateral acceleration sensors and steering hand-wheel angle sensors, that are used to help provide the stability control of the vehicle. For example, certain vehicle stability systems employ differential braking in response to an undesired turning or yaw of the vehicle. Other vehicle stability systems employ active front-wheel or rear-wheel steering that assist the vehicle operator in steering the vehicle in response to the detected rotation of the steering wheel. Other vehicle stability systems employ active suspension stability systems that change the vehicle suspension in response to road conditions and other vehicle operating conditions.
If any of the sensors, actuators and sub-systems associated with these stability systems fail, it is desirable to quickly detect the fault and activate fail-safe strategies so as to prevent the system from improperly responding to a perceived, but false condition. It is also desirable to isolate the defective sensor, actuator or sub-system for maintenance and replacement purposes, and also select the proper fail-safe action for the problem. Thus, it is necessary to monitor the various sensors, actuators and sub-systems employed in these stability systems to identify a failure.